JP5424813B2 - Wireless communication system and wireless communication relay device - Google Patents

Description

  The present invention relates to a radio communication system in which a plurality of relay stations perform signal transfer in cooperation between a transmission-side communication apparatus and a reception-side communication apparatus, and a radio communication relay apparatus that operates as a relay station.

  In recent years, a cooperative diversity technique for obtaining diversity in relay transmission by operating a plurality of relay stations in cooperation has been actively studied. Among them, a technique that applies space-time block codes (STBC) in relay processing is known as a highly effective technique (see Patent Document 1 below).

US Patent Application Publication No. 2008/0175184

  However, the technique described in Patent Document 1 assumes a single transfer between two devices (base station and mobile station) that perform communication. Need to be sequentially demodulated in each relay device that transfers (relays) In particular, when MIMO (Multiple-Input Multiple-Output) is applied, signal separation is required in each relay process, so that a plurality of antennas and amplifiers are required, and the cost of the relay apparatus increases. In addition to these hardware problems of the relay device, when MIMO is applied, the channel between the devices is required to be a channel capable of signal separation. Therefore, when the technique described in Patent Document 1 is applied to an ad hoc network or the like, there is a problem that the number of terminals that cannot participate in the network increases.

  The present invention has been made in view of the above, and eliminates the need for complete demodulation processing (signal separation) in each relay apparatus even when STBC is applied and multistage transfer is performed. It is an object of the present invention to obtain a wireless communication system that realizes transfer that can be demodulated collectively by a communication device.

  In order to solve the above-described problem and achieve the object, the present invention relays a signal transmitted from a first wireless communication device by a plurality of wireless communication relay devices and transmits the signal to a second wireless communication device. In the communication system, each of the plurality of wireless communication relay devices receives a received signal so as to obtain space diversity in the second wireless communication device in cooperation with another wireless communication relay device when relaying a received signal. The signal is encoded.

  According to the present invention, communication quality can be improved. In addition, each wireless communication relay device does not require processing for separating signals when relaying signals, so that an increase in the number of devices and complexity of processing can be prevented.

FIG. 1 is a diagram showing a configuration example of a first embodiment of a wireless communication system according to the present invention. FIG. 2 is a diagram illustrating a configuration example of the communication apparatus illustrated in FIG. FIG. 3 is a diagram illustrating a configuration example of the relay apparatus illustrated in FIG. FIG. 4 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the first embodiment. FIG. 5 is a diagram illustrating a configuration example of the second embodiment of the wireless communication system according to the present invention. FIG. 6 is a diagram illustrating a configuration example of the communication apparatus illustrated in FIG. FIG. 7 is a diagram illustrating a configuration example of the relay apparatus illustrated in FIG. FIG. 8 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the second embodiment. FIG. 9 is a diagram illustrating a configuration example of a third embodiment of the wireless communication system according to the present invention. FIG. 10 is a diagram illustrating a configuration example of the communication device on the reception side illustrated in FIG. FIG. 11 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the third embodiment. FIG. 12 is a diagram illustrating a modification of the wireless communication system according to the third embodiment. FIG. 13 is a diagram illustrating a modification of the wireless communication system according to the third embodiment. FIG. 14 is a diagram illustrating a configuration example of a relay device included in the wireless communication system illustrated in FIG. 13. FIG. 15 is a diagram illustrating a configuration example of a fourth embodiment of the wireless communication system according to the present invention. FIG. 16 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the fourth embodiment.

  Embodiments of a wireless communication system and a wireless communication relay device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a first embodiment of a wireless communication system according to the present invention. As shown in the figure, the wireless communication system of the present embodiment transmits signals between two wireless communication devices (hereinafter simply referred to as communication devices) 1-1 and 1-2 that perform communication, and these communication devices. A plurality of wireless communication relay devices (hereinafter simply referred to as relay devices) 2-1 to 2-4 for relaying.

  In the present embodiment, the communication device 1-1 is described as a transmission-side communication device, and the communication device 1-2 is described as a reception-side communication device. The relay apparatuses 2-1 and 2-2 receive and relay the signal transmitted from the communication apparatus 1-1, and the signals relayed by the relay apparatuses 2-1 and 2-2 are relayed. The operation when 2-4 receives and relays, and the communication apparatus 1-2 receives signals relayed by the relay apparatuses 2-3 and 2-4 will be described.

  FIG. 2 is a diagram illustrating a configuration example of the communication device 1 corresponding to the communication devices 1-1 and 1-2 illustrated in FIG. As illustrated, the communication device 1 includes an antenna 11, a reception unit 12, and a transmission unit 13, which are connected by a signal line 14. When receiving a signal, the communication device 1 transmits the signal received from the antenna 11 to the receiving unit 12 via the signal line 14 and performs a predetermined reception process. When transmitting a signal, the transmission unit 13 generates a transmission signal and transmits it to the antenna 11 via the signal line 14. The antenna 11 transmits the transmission signal received from the transmission unit 13.

  FIG. 3 is a diagram illustrating a configuration example of the relay device 2 corresponding to the relay devices 2-1 to 2-4 illustrated in FIG. As illustrated, the relay device 2 includes an antenna 21, a reception unit 22, a transmission unit 23 and an encoding unit 24, and the antenna 21, the reception unit 22 and the transmission unit 23 are connected by a signal line 25. Also. The receiving unit 22 and the encoding unit 24 are connected by a signal line 26, and the transmitting unit 23 and the encoding unit 24 are connected by a signal line 27. In the relay device 2, when relaying the received signal, the signal received by the antenna 21 is transmitted to the receiving unit 22 via the signal line 25 and predetermined reception processing is performed. Then, the signal obtained by the reception process in the reception unit 22 is transmitted to the encoding unit 24 via the signal line 26 and is encoded. The encoded signal is transmitted to the transmission unit 23 via the signal line 27, and the transmission unit 23 performs a predetermined transmission process on the signal received from the encoding unit 24 to generate a transmission signal. The generated transmission signal is transmitted to the antenna 21 via the signal line 25 and transmitted from the antenna 21.

  A signal transmission operation in the radio communication system of the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the first embodiment, and illustrates a signal transmission operation from the communication device 1-1 to the communication device 1-2 in FIG.

First, the communication device 1-1 generates and transmits a signal (step S11). Specifically, a signal is generated by the transmission unit 13 in the communication device 1-1, transmitted from the signal line 14 to the antenna 11, and transmitted from the antenna 11. Here, it is assumed that four symbols are handled as a set of signal vectors, and the baseband signal generated by the transmission unit 13 is expressed as s ₁ ⁽¹⁾ = [s _1,1 ⁽¹⁾ , s _1,2 ⁽¹⁾ , S _1,3 ⁽¹⁾ , s _1,4 ⁽¹⁾ ] ^T. Each signal of this signal vector is transmitted in the same frequency band, and the index p in s _{1, p} ^{(1) T} (p = 1 to 4) is given along the time direction. T represents transposition.

  The j-th (j = 1, 2) relay devices (relay devices 2-1 and 2-2) that receive signals at the first hop receive the signals transmitted from the communication device 1-1 (step S12). ). In the following description, the index of a device (communication device, relay device) that performs transmission processing at each hop is i, and the index of a device (communication device, relay device) that performs reception processing is j.

The receiving operation (the operation of step S12) in the relay apparatuses 2-1 and 2-2 that receive the signal of the first hop will be described in more detail. In these relay apparatuses, the signal is received from the antenna 21, and the signal Is transmitted to the receiver 22 via the signal line 25. The receiving unit 22 performs predetermined reception processing on the signal received from the antenna 21 and receives a received signal vector r _j ⁽¹⁾ = [r _{j, 1} ⁽¹⁾ , r _{j, 2} ^{( 1)} , r _{j, 3} ⁽¹⁾ , r _{j, 4} ⁽¹⁾ ] ^T Each received signal r _{j, p} ⁽¹⁾ (p = 1 to 4) is given by the following equation (1).

Here, h _j1 ⁽¹⁾ represents the impulse response of the transmission line from the communication device 1-1 to the jth (j = 1, 2) relay device, and n _{j, p} ⁽¹⁾ represents the jth This noise is added to the signal h _j1 ⁽¹⁾ s _{1, p} ⁽¹⁾ by the relay device. The obtained signal of the above formula (1) is transmitted to the encoding unit 24 via the signal line 26, and the encoding unit 24 performs encoding, which is characteristic processing in the wireless communication system of the present embodiment. (Step S13).

  The encoding process executed in step S13 will be described in detail.

In the encoding unit 24 of the relay apparatus 2-1, r ₁ ⁽¹⁾ = [r _1,1 ⁽¹⁾ , r _1,2 ⁽¹⁾ , r _1,3 ⁽¹⁾ , r _1,4 ⁽¹⁾ ] ^{T is} encoded to obtain a transmission signal vector s ₁ ^{(2) represented} by the following equation (2).

Further, in the encoding unit 24 of the relay apparatus 2-2, r ₂ ⁽¹⁾ = [r _2,1 ⁽¹⁾ , r _2,2 ⁽¹⁾ , r _2,3 ^{(1 )} , R _2,4 ⁽¹⁾ ] ^{T is} encoded to obtain a transmission signal vector s ₂ ^{(2) represented} by the following equation (3).

Here, * represents a complex conjugate. In the encoding units 24 of the relay apparatuses 2-1 and 2-2, a known space-time code (STBC) is used for the _two input signal vectors (r ₁ ⁽¹⁾ , r ₂ ⁽¹⁾ ). Each of the signal vectors is generated in the same way as when (Codes) is implemented. That is, the encoding units 24 of the relay devices cooperate to perform space-time encoding. It should be noted that the coefficient (1 / √2) multiplied by the encoding process in each encoding unit 24 is simultaneously (1) because there are two relay devices (the signals are relayed by the two relay devices). The purpose is to normalize the total transmission power from each relay device that relays (at the hop).

Respective transmission signals s _i ⁽²⁾ = [s _{i, 1} ⁽²⁾ , s _{i, 2} ⁽²⁾ obtained by encoding by the encoding units 24 of the relay apparatuses 2-1 and 2-2. , S _{i, 3} ⁽²⁾ , s _{i, 4} ⁽²⁾ ] ^T (i = 1, 2) are transmitted to the transmission unit 23 via the signal line 27 and subjected to transmission processing by the transmission unit 23. Then, the signal is transmitted via the signal line 25 and the antenna 21 (step S14).

  The j-th (j = 1, 2) relay device (relay device 2-3, 2-4) of the second hop that receives the signal transmitted in step S14 is the first-hop relay device 2-1, Each of the signals transmitted from 2-2 is received (step S15).

In the relay apparatuses 2-3 and 2-4 that receive the signal of the second hop, the signal received by the antenna 21 is transmitted to the receiving unit 22 via the signal line 25, and the receiving unit 22 performs predetermined processing on the received signal. The received signal vector r _j ⁽²⁾ = [r _{j, 1} ⁽²⁾ , r _{j, 2} ⁽²⁾ , r _{j, 3} ⁽²⁾ , r _{j, 4} ⁽²⁾ ] Get ^T. Each received signal r _{j, p} ⁽²⁾ (p = 1 to 4) is given by the following equation (4).

Here, h _ji ⁽²⁾ receives the signal at the second hop from the i-th (i = 1,2) relay device (relay devices 2-1 and 2-2) that transfers the signal at the first hop. Represents the impulse response of the transmission line up to the j-th (j = 1, 2) relay device (relay devices 2-3, 2-4), and n _{j, p} ⁽²⁾ is the signal at the j-th relay device. This is the noise added to h _j1 ⁽²⁾ s _{1, p} ⁽²⁾ + h _j2 ⁽²⁾ s _{2, p} ⁽²⁾ . The obtained signal of the above formula (4) is transmitted to the encoding unit 24 via the signal line 26, and the encoding unit 24 performs encoding, which is characteristic processing in the wireless communication system of the present embodiment. (Step S16).

  The encoding process executed in step S16 will be described in detail.

In the encoding unit 24 of the relay apparatus 2-3, r ₁ ⁽²⁾ = [r _1,1 ⁽²⁾ , r _1,2 ⁽²⁾ , r _1,3 ⁽²⁾ , r _1,4 ⁽²⁾ ] ^{T is} encoded to obtain a transmission signal vector s ₁ ^{(3) represented} by the following equation (5).

In the encoding unit 24 of the relay apparatus 2-4, r ₂ ⁽²⁾ = [r _2,1 ⁽²⁾ , r _2,2 ⁽²⁾ , r _2,3 ^{(2 )} , R _2,4 ⁽²⁾ ] ^{T is} encoded to obtain a transmission signal vector s ₂ ^{(3) represented} by the following equation (6).

Here, in the encoding units 24 of the relay apparatuses 2-3 and 2-4, a space-time code having two symbols as a unit for the two input signal vectors (r ₁ ⁽²⁾ , r ₂ ⁽²⁾ ). A signal vector equivalent to the case where the conversion is performed is generated. That is, the encoding units 24 of the relay devices cooperate to perform space-time encoding in units of 2 symbols. In this way, in the encoding unit 24 in each hop relay device, the range of the encoding processing target (a symbol unit for performing space-time encoding in cooperation with other relay devices) is changed. It is the characteristic in the radio | wireless communications system of embodiment. For example, as described above, normal space-time coding is performed in the first-hop relay processing (relay device), and space-time coding is performed in units of two symbols in the second hop relay processing. The coefficient (1 / √2) multiplied by the encoding process in each encoding unit 24 of relay apparatuses 2-3 and 2-4 is the same as that of relay apparatuses 2-1 and 2-2 of the first hop. In addition, the total transmission power is normalized according to the number of relay devices (two in this example).

Respective transmission signals s _i ⁽³⁾ = [s _{i, 1} ⁽³⁾ , s _{i, 2} ⁽³⁾ obtained by encoding by the encoding units 24 of the relay apparatuses 2-3 and 2-4 , S _{i, 3} ⁽³⁾ , s _{i, 4} ⁽³⁾ ] ^T (i = 1, 2) are transmitted to the transmission unit 23 via the signal line 27 and subjected to transmission processing by the transmission unit 23. The signal is transmitted via the signal line 25 and the antenna 21 (step S17).

  Then, the communication device 1-2 which is the communication device on the receiving side receives the signal transmitted in step S17, that is, the signal transmitted from each of the second-hop relay devices 2-3 and 2-4 (step S18).

The operation of the communication device 1-2 in step S18 will be described in more detail. In the communication device 1-2, a signal received by the antenna 11 is transmitted to the receiving unit 12 via the signal line 14. The receiving unit 12 performs predetermined reception processing on the signal received from the antenna 11 and receives a received signal vector r ₁ ⁽³⁾ = [r _1,1 ⁽³⁾ , r _1,2 ^{( 3)} , r _1,3 ⁽³⁾ , r _1,4 ⁽³⁾ ] ^T Each received signal r _{1, p} ⁽³⁾ (p = 1 to 4) is given by the following equation (7).

Here, h _ji ⁽³⁾ is from the i-th (i = 1, 2) relay device (relay device 2-3, 2-4) that transfers the signal at the second hop to the communication device 1-2. This represents the impulse response of the transmission line, and n _{j, p} ⁽³⁾ is added to the signal h _j1 ⁽³⁾ s _{1, p} ⁽³⁾ + h _j2 ⁽³⁾ s _{2, p} ⁽³⁾ by the communication device 1-2. Noise.

Subsequently, characteristic operations in the wireless communication system of the present embodiment will be described. When the relay devices 2-1 to 2-4 perform the signal relay processing including the encoding processing described above, the received signal vector r ₁ ⁽³⁾ received by the communication device 1-2 is expressed by the following equation (8). Can be expressed as:

At this time, the signal block S of the equation (8) has a structure equivalent to a known quasi-orthogonal space-time block coding (QOSTBC). Therefore, it is possible to obtain space diversity that has an effect of reducing the influence of attenuation on the signal of the propagation path. Then, when reception processing such as known maximum likelihood determination reception is performed on the received signal vector r ₁ ⁽³⁾ , a higher reliability determination is performed compared to a case where diversity is not obtained. can do. This is because, in the encoding process performed by the encoding unit 24 of each relay apparatus (relay apparatuses 2-1 to 2-4), the unit (number of symbols) for encoding and rearranging signals is changed for each hop. This is because an interference suppression effect can be obtained at each hop, and the communication apparatus 1-2 can receive signals while suppressing interference between signals.

  Note that a signal block having a pseudo-orthogonal space-time code structure can be configured by a method different from the above-described encoding method. In the above description, normal space-time coding processing is performed in the first-hop relay devices 2-1 and 2-2, and two symbols are used as one unit in the second-hop relay devices 2-3 and 2-4. In spite of this, the space-time coding process was performed, but on the contrary, the 1-hop relay devices 2-1 and 2-2 performed the space-time coding process with 2 symbols as a unit, and the second-hop relay. The devices 2-3 and 2-4 may be configured to perform normal space-time coding processing. Specifically, the encoding units 24 of the first-hop relay apparatuses 2-1 and 2-2 perform the encoding process represented by the following equation (9).

  In addition, the encoding units 24 of the second-hop relay apparatuses 2-3 and 2-4 respectively perform the encoding process represented by the following equation (10).

  That is, if the receiving-side communication device 1-2 is configured to receive the signal vector represented by the above equation (8), the encoding unit 24 of each relay device encodes the signal. -The correspondence between the unit for rearranging and the number of hops may be arbitrary.

  Moreover, you may comprise the quasi-orthogonal space-time code of the structure different from said Formula (8). For example, the encoding units 24 of the first-hop relay apparatuses 2-1 and 2-2 each perform the encoding process represented by the following equation (11).

  In addition, the encoding units 24 of the second-hop relay apparatuses 2-3 and 2-4 respectively perform the encoding process represented by the following equation (12).

  When such encoding is performed, a signal vector received by the communication device 1-2 is expressed by the following equation (13). In addition, g is the same as what was shown by Formula (8).

  Even with such a coding structure, the effect of space diversity can be obtained. Further, as encoding, it is possible to perform processing such as encoding / replacement of a real part and an imaginary part of a signal individually and no transmission.

  In this embodiment, the index p is given along the time direction. However, the index p is given in the frequency direction, the encoding process is performed in the frequency domain, and the signal received by the communication device on the receiving side is Alternatively, a configuration equivalent to a known quasi-orthogonal space-frequency block coding (QOSFBC) may be used. Further, for example, encoding may be performed using both time and frequency domains, such that the first encoding is performed in the time domain and the second encoding is performed in the frequency domain.

  As described above, in the wireless communication system according to the present embodiment, when two-hop relay transmission is performed in cooperation with a plurality of relay apparatuses, a coding process for generating a coded signal such as a pseudo orthogonal space-time code is divided. Thus, the encoding process is performed in which each hop relay apparatus is divided. In addition, each relay apparatus performs space-time encoding processing with different encoding units for each hop. Thereby, space diversity can be obtained and communication quality can be improved. Further, since each relay device does not need to separate signals, it is possible to prevent the number of devices from increasing and the processing complexity.

  In this embodiment, an example in which the number of hops is 2 has been described. However, the present embodiment can also be applied to a case in which there are 3 or more hops as described in other embodiments described later.

Embodiment 2. FIG.
Next, the radio communication system according to the second embodiment will be described. In Embodiment 1, the wireless communication system in which the relay device relays the signal twice between the communication device on the transmission side and the communication device on the reception side has been described. A wireless communication system having a larger number of hops than the first embodiment will be described.

  FIG. 5 is a diagram illustrating a configuration example of the second embodiment of the wireless communication system according to the present invention. As illustrated, the communication system according to the present embodiment includes two 1a-1 and 1a-2 that perform communication, and a plurality of relay devices 2a-1 to 2a-6 that relay signals between these communication devices. It consists of.

  In the present embodiment, the communication device 1a-1 is described as a transmission-side communication device, and the communication device 1a-2 is described as a reception-side communication device. Further, the relay devices 2a-1 and 2a-2 receive and relay the signal transmitted from the communication device 1a-1, and the signals relayed by the relay devices 2a-1 and 2a-2 are relayed to the relay device 2a-3 and 2a-4 receives and relays, and relays 2a-5 and 2a-6 receive and relay the signals relayed by relays 2a-3 and 2a-4, and relays 2a-5 and 2a The operation when the communication device 1a-2 receives the signal relayed in −6, that is, the wireless communication system in which the number of relays (the number of hops) is 3 will be described.

  FIG. 6 is a diagram illustrating a configuration example of the communication device 1a corresponding to the communication devices 1a-1 and 1a-2 illustrated in FIG. In addition, the same code | symbol is attached | subjected to the same component as the communication apparatus 1 (refer FIG. 2) demonstrated in Embodiment 1. FIG. As illustrated, the communication device 1a of the present embodiment is obtained by replacing the reception unit 12 and the transmission unit 13 included in the communication device 1 of the first embodiment with a reception unit 12a and a transmission unit 13a. In the present embodiment, only parts different from the communication device 1 of the first embodiment will be described.

  In communication device 1a, reception unit 12a further executes processing for converting a signal from the time domain to the frequency domain in addition to the reception processing performed by reception unit 12 in communication device 1 of the first embodiment. The transformation from the time domain to the frequency domain is performed using, for example, a discrete Fourier transform (DFT). In addition to the transmission process performed by the transmission unit 13 in the communication device 1, the transmission unit 13a further executes a process of converting the signal from the frequency domain to the time domain. The transformation from the frequency domain to the time domain is performed using, for example, an inverse discrete Fourier transform (IDFT).

  FIG. 7 is a diagram illustrating a configuration example of the relay apparatus 2a corresponding to the relay apparatuses 2a-1 to 2a-6 illustrated in FIG. In addition, the same code | symbol is attached | subjected to the same component as the relay apparatus 2 (refer FIG. 3) demonstrated in Embodiment 1. FIG. As illustrated, the relay device 2a according to the present embodiment includes the reception unit 22, the transmission unit 23, and the encoding unit 24 included in the relay device 2 according to the first embodiment, the reception unit 22a, the transmission unit 23a, and the code. It is replaced with the conversion unit 24a. In the present embodiment, only parts different from the relay apparatus 2 of the first embodiment will be described.

  In relay device 2a, reception unit 22a further executes a process of converting a signal from the time domain to the frequency domain in addition to the reception process performed by reception unit 22 in relay device 2 of the first embodiment. In addition to the transmission process performed by the transmission unit 23 in the relay device 2, the transmission unit 23a further executes a process of converting the signal from the frequency domain to the time domain. Also, unlike the encoding unit 24 of the relay device 2, the encoding unit 24a performs encoding processing in the frequency domain.

  In the radio communication system according to the present embodiment, the radio communication system according to the first embodiment is characterized in that radio signal relaying (the number of hops) and encoding processing in relay apparatuses 2a-1 to 2a-6 are performed in the frequency domain. And different.

  A signal transmission operation in the wireless communication system of the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the present embodiment, and illustrates a signal transmission operation from communication device 1a-1 to communication device 1a-2 in FIG. Note that the processes in steps S11a to S18a in FIG. 8 correspond to the processes in steps S11 to S18 described in the first embodiment, and are necessary for performing the encoding process in each relay apparatus in the frequency domain. It is a process added. However, in the wireless communication system of the present embodiment, 8 symbols are handled as a set of signal vectors.

First, the communication device 1a-1 generates and transmits a signal (step S11a). Specifically, the transmission unit 13 a generates a frequency-domain baseband signal, further converts the signal into a time-domain signal, transmits the signal to the antenna 11 through the signal line 14, and transmits the signal from the antenna 11. Here, the transmission unit 13a uses the baseband signal as s ₁ ⁽¹⁾ = [s _1,1 ⁽¹⁾ , s _1,2 ⁽¹⁾ , s _1,3 ⁽¹⁾ , s _1,4 ⁽¹⁾ , s _1,5 ⁽¹⁾ , s _1,6 ⁽¹⁾ , s _1,7 ⁽¹⁾ , s _1,8 ⁽¹⁾ ] ^T shall be generated. Each signal of this signal vector is transmitted at the same time, and an index p in s _{1, p} ^{(1) T} (p = 1 to 8) is given along the frequency direction.

The j-th (j = 1, 2) relay device (relay devices 2a-1, 2a-2) that receives a signal at the first hop receives the signal transmitted from the communication device 1a-1 (step S12a). ). Specifically, the relay devices 2 a-1 and 2 a-2 receive a signal from the antenna 21, and the signal is transmitted to the receiving unit 22 a via the signal line 25. The receiving unit 22a performs predetermined reception processing on the received signal, and receives a received signal vector r _j ⁽¹⁾ = [r _{j, 1} ⁽¹⁾ , r _{j, 2} ^{( 1)} , r _{j, 3} ⁽¹⁾ , r _{j, 4} ⁽¹⁾ , r _{j, 5} ⁽¹⁾ , r _{j, 6} ⁽¹⁾ , r _{j, 7} ⁽¹⁾ , r _{j, 8} ⁽¹⁾ ] Get ^T Each received signal r _{j, p} ⁽¹⁾ (p = 1 to 8) is given by the following equation (14).

Here, h _j1 ⁽¹⁾ represents the impulse response of the transmission path from the communication device 1a-1 to the jth (j = 1, 2) relay device, and n _{j, p} ⁽¹⁾ represents the jth This noise is added to the signal h _j1 ⁽¹⁾ s _{1, p} ⁽¹⁾ by the relay device. The obtained signal of the formula (14) is transmitted to the encoding unit 24a via the signal line 26, and the encoding unit 24a performs encoding (step S13a).

  The encoding process executed in step S13a will be described in detail.

In the encoding unit 24a of the relay apparatus 2a-1, r ₁ ⁽¹⁾ = [r _1,1 ⁽¹⁾ , r _1,2 ⁽¹⁾ , r _1,3 ⁽¹⁾ , r _1,4 ^(1), performs encoding with respect to ^{_{r 1,5 (1), r 1,6}} (1), r 1,7 (1), r 1,8 (1)] T, the following A transmission signal vector s ₁ ^{(2) represented} by Expression (15) is obtained.

Further, in the encoding unit 24a of the relay device 2a-2, r ₂ ⁽¹⁾ = [r _2,1 ⁽¹⁾ , r _2,2 ⁽¹⁾ , r _2,3 ^{(1 )} input from the receiving unit 22a. ^{_{), r 2,4 (1),}} r 2,5 (1), r 2,6 (1), r 2,7 (1), performs encoding with respect to r _2,8 ^{(1)] T} The transmission signal vector s ₂ ⁽²⁾ expressed by the following equation (16 ⁾ is obtained.

Here, in the encoding units 24a of the relay apparatuses 2a-1 and 2a-2, space-time encoding is performed on the two input signal vectors (r ₁ ⁽¹⁾ , r ₂ ⁽¹⁾ ). Respectively, is generated. That is, each encoding unit 24a of each relay apparatus performs space-time encoding in cooperation. Note that the coefficient (1 / √2) multiplied in the encoding process in each encoding unit 24a is the same as that in the encoding unit 24 described in the first embodiment (at the first hop). This is intended to normalize the total transmission power from each relay device that performs relaying.

Respective transmission signals s _i ⁽²⁾ = [s _{i, 1} ⁽²⁾ , s _{i, 2} ⁽²⁾ obtained by the encoding unit 24a of the relay apparatuses 2a-1 and 2a-2 executing the encoding , S _{i, 3} ⁽²⁾ , s _{i, 4} ⁽²⁾ , s _{i, 5} ⁽²⁾ , s _{i, 6} ⁽²⁾ , s _{i, 7} ⁽²⁾ , s _{i, 8} ⁽²⁾ ] ^T (i = 1, 2) is transmitted to the transmission unit 23 a via the signal line 27, is subjected to transmission processing by the transmission unit 23 a and converted into a time domain signal, and then passes through the signal line 25 and the antenna 21. (Step S14a).

The second-hop j-th (j = 1, 2) relay device (relay devices 2a-3, 2a-4) that receives the signal transmitted in step S14a is connected to the first-hop relay device 2a-1, Each of the signals transmitted from 2a-2 is received (step S15a). Specifically, the relay devices 2 a-3 and 2 a-4 receive a signal from the antenna 21, and the signal is transmitted to the receiving unit 22 a via the signal line 25. The receiving unit 22a performs predetermined reception processing on the received signal, and receives a received signal vector r _j ⁽²⁾ = [r _{j, 1} ⁽²⁾ , r _{j, 2} ^{( 2)} , r _{j, 3} ⁽²⁾ , r _{j, 4} ⁽²⁾ , r _{j, 5} ⁽²⁾ , r _{j, 6} ⁽²⁾ , r _{j, 7} ⁽²⁾ , r _{j, 8} ⁽²⁾ ] Get ^T Each received signal r _{j, p} ⁽²⁾ (p = 1 to 8) is given by the following equation (17).

Here, h _ji ⁽²⁾ receives the signal at the second hop from the i-th (i = 1, 2) relay device (relay device 2a-1, 2a-2) that transfers the signal at the first hop. Represents the impulse response of the transmission path to the jth (j = 1, 2) relay device (relay devices 2a-3, 2a-4), and n _{j, p} ⁽²⁾ is a signal at the jth relay device. This is the noise added to h _j1 ⁽²⁾ s _{1, p} ⁽²⁾ + h _j2 ⁽²⁾ s _{2, p} ⁽²⁾ . The obtained signal of the above equation (17) is transmitted to the encoding unit 24a via the signal line 26, and the encoding unit 24a performs encoding (step S16a).

  The encoding process executed in step S16a will be described in detail.

In the encoding unit 24a of the relay apparatus 2a-3, r ₁ ⁽²⁾ = [r _1,1 ⁽²⁾ , r _1,2 ⁽²⁾ , r _1,3 ⁽²⁾ , ^{_{r 1,4 (2), r 1,5}} (2), r 1,6 (2), r 1,7 (2), performs encoding on r _1,8 ^{(2)] T,} the following A transmission signal vector s ₁ ^{(3) represented} by Expression (18) is obtained.

Further, in the encoding unit 24a of the relay apparatus 2a-4, r ₂ ⁽²⁾ = [r _2,1 ⁽²⁾ , r _2,2 ⁽²⁾ , r _2,3 ^{(2 )} input from the receiving unit 22a. ^{_{), r 2,4 (2),}} r 2,5 (2), r 2,6 (2), r 2,7 (2), performs encoding on r _2,8 ^{(2)] T} Then, a transmission signal vector s ₂ ⁽³⁾ expressed by the following equation (19 ⁾ is obtained.

Here, in the encoding unit 24a of the relay apparatuses 2a-3 and 2a-4, a space-time code having two symbols as a unit for the two input signal vectors (r ₁ ⁽²⁾ , r ₂ ⁽²⁾ ). A signal vector equivalent to the case where the conversion is performed is generated. As described above, in this embodiment as well, in the first-hop and second-hop relay apparatuses, the range to be subjected to space-time coding processing (units of symbols for space-time coding) To change. Note that the coefficient (1 / √2) multiplied by the encoding process in each encoding unit 24a of the relay apparatuses 2a-3 and 2a-4 is the same as that of the first-hop relay apparatuses 2a-1 and 2a-2. In addition, the total transmission power is normalized according to the number of relay devices (two in this example).

Respective transmission signals s _i ⁽³⁾ = [s _{i, 1} ⁽³⁾ , s _{i, 2} ⁽³⁾ obtained by the encoding unit 24a of the relay apparatuses 2a-3 and 2a-4 executing the encoding , S _{i, 3} ⁽³⁾ , s _{i, 4} ⁽³⁾ , s _{i, 5} ⁽³⁾ , s _{i, 6} ⁽³⁾ , s _{i, 7} ⁽³⁾ , s _{i, 8} ⁽³⁾ ] ^T (i = 1, 2) is transmitted to the transmission unit 23 a via the signal line 27, is subjected to transmission processing by the transmission unit 23 a and converted into a time domain signal, and then passes through the signal line 25 and the antenna 21. (Step S17a).

Next, the j-th (j = 1, 2) relay device (relay devices 2a-5, 2a-6) of the third hop that receives the signal transmitted in step S17a is the second hop relay device 2a. The signals transmitted from -3 and 2a-4 are respectively received (step S21). Specifically, the relay devices 2 a-5 and 2 a-6 receive a signal from the antenna 21, and the signal is transmitted to the receiving unit 22 a via the signal line 25. The receiving unit 22a performs predetermined reception processing on the received signal, and receives a received signal vector r _j ⁽³⁾ = [r _{j, 1} ⁽³⁾ , r _{j, 2} ^{( 3)} , r _{j, 3} ⁽³⁾ , r _{j, 4} ⁽³⁾ , r _{j, 5} ⁽³⁾ , r _{j, 6} ⁽³⁾ , r _{j, 7} ⁽³⁾ , r _{j, 8} ⁽³⁾ ] Get ^T Each received signal r _{j, p} ⁽³⁾ (p = 1 to 8) is given by the following equation (20).

Here, h _ji ⁽³⁾ receives the signal at the third hop from the i-th (i = 1, 2) relay device (relay devices 2a-3, 2a-4) that transfers the signal at the second hop. Represents the impulse response of the transmission path to the jth (j = 1, 2) relay device (relay devices 2a-5, 2a-6), and n _{j, p} ⁽³⁾ is the signal at the jth relay device. This is the noise added to h _j1 ⁽³⁾ s _{1, p} ⁽³⁾ + h _j2 ⁽³⁾ s _{2, p} ⁽³⁾ . The obtained signal of the above equation (20) is transmitted to the encoding unit 24a via the signal line 26, and the encoding unit 24a performs encoding (step S22).

  The encoding process executed in step S22 will be described in detail.

In the encoding unit 24a of the relay apparatus 2a-5, r ₁ ⁽³⁾ = [r _1,1 ⁽³⁾ , r _1,2 ⁽³⁾ , r _1,3 ⁽³⁾ , ^{_{r 1,4 (3), r 1,5}} (3), r 1,6 (3), r 1,7 (3), performs encoding on r _1,8 ^{(3)] T,} the following A transmission signal vector s ₁ ^{(4) represented} by Expression (21) is obtained.

Further, in the encoding unit 24a of the relay apparatus 2a-6, r ₂ ⁽³⁾ = [r _2,1 ⁽³⁾ , r _2,2 ⁽³⁾ , r _2,3 ^{(3 _{), r 2,4 (3),}} r 2,5 (3), r 2,6 (3), r 2,7 (3), performs encoding on r _2,8 ^{(3)] T} Then, a transmission signal vector s ₂ ⁽⁴⁾ expressed by the following equation (22 ⁾ is obtained.

Here, in the encoding units 24 of the relay apparatuses 2a-5 and 2a-6, a space-time code in units of 4 symbols with respect to the _two input signal vectors (r ₁ ⁽³⁾ , r ₂ ⁽³⁾ ). A signal vector equivalent to the case where the conversion is performed is generated. As described above, in this embodiment as well, in each hop relay apparatus, the range of processing objects of space-time coding (the unit of symbols for space-time coding) is changed in each hop relay apparatus. For example, as described above, normal space-time coding is performed in the first-hop relay processing (relay device), and space-time coding is performed in units of two symbols in the second hop relay processing. In the hop relay process, space-time coding is performed in units of 4 symbols. Note that the coefficient (1 / √2) multiplied by the encoding process in each encoding unit 24a of the relay apparatuses 2a-5 and 2a-6 is the same as that of the first and second hop relay apparatuses. This is for normalizing the total transmission power in accordance with the number (two in this example).

Respective transmission signals s _i ⁽⁴⁾ = [s _{i, 1} ⁽⁴⁾ , s _{i, 2} ⁽⁴⁾ obtained by the encoding unit 24a of the relay apparatuses 2a-5 and 2a-6 executing the encoding , S _{i, 3} ⁽⁴⁾ , s _{i, 4} ⁽⁴⁾ , s _{i, 5} ⁽⁴⁾ , s _{i, 6} ⁽⁴⁾ , s _{i, 7} ⁽⁴⁾ , s _{i, 8} ⁽⁴⁾ ] ^T (i = 1, 2) is transmitted to the transmission unit 23 a via the signal line 27, is subjected to transmission processing by the transmission unit 23 a and converted into a time domain signal, and then passes through the signal line 25 and the antenna 21. (Step S23).

  Then, the communication device 1a-2, which is the communication device on the receiving side, receives the signal transmitted in step S23, that is, the signal transmitted from each of the relay devices 2a-5 and 2a-6 of the third hop (step S23). S18a).

The operation of the communication device 1a-2 in step S18a will be described in more detail. In the communication device 1a-2, a signal received by the antenna 11 is transmitted to the receiving unit 12a via the signal line 14. The receiving unit 12a performs predetermined reception processing on the received signal, and a received signal vector r ₁ ⁽⁴⁾ = [r _1,1 ⁽⁴⁾ , r _1,2 ^{( 4)} , r _1,3 ⁽⁴⁾ , r _1,4 ⁽⁴⁾ , r _1,5 ⁽⁴⁾ , r _1,6 ⁽⁴⁾ , r _1,7 ⁽⁴⁾ , r _1,8 ⁽⁴⁾ ] Get ^T Each received signal r _{1, p} ⁽⁴⁾ (p = 1 to 8) is given by the following equation (23).

Here, h _ji ⁽⁴⁾ is from the i-th (i = 1, 2) relay device (relay devices 2a-5, 2a-6) that transfers signals at the third hop to the communication device 1a-2. Represents the impulse response of the transmission line, and n _{j, p} ⁽⁴⁾ is added to signal h _j1 ⁽⁴⁾ s _{1, p} ⁽⁴⁾ + h _j2 ⁽⁴⁾ s _{2, p} ⁽⁴⁾ in communication device 1a-2 Noise.

Subsequently, characteristic operations in the wireless communication system of the present embodiment will be described. When the relay devices 2a-1 to 2a-6 execute the signal relay processing including the encoding processing described above, the received signal vector r ₁ ⁽⁴⁾ in the frequency domain received by the communication device 1a-2 is expressed by the following equation ( 24).

At this time, the signal block S of Expression (24) is the same as the signal block S of the received signal vector (see Expression (8)) received by the communication device 1-2 on the reception side of the wireless communication system shown in Embodiment 1. Similarly, it has a structure equivalent to a quasi-orthogonal space-time code. Therefore, it is possible to obtain space diversity that has an effect of reducing the influence of attenuation on the signal of the propagation path. When receiving processing such as maximum likelihood determination reception is performed on the received signal vector r ₁ ⁽⁴⁾ , it is possible to perform highly reliable determination as compared to the case where no diversity is obtained. it can.

  As described above, in the wireless communication system of the present embodiment, the number of hops is increased as compared with the wireless communication system of the first embodiment, and accordingly, in the relay devices 2a-5 and 2a-6 at the third hop, a code is added. It was decided to increase the number of units for performing the conversion process and to obtain space diversity effectively. In this embodiment, the number of hops is 3 hops. However, when multi-hop transmission with 4 hops or more is performed, the encoding process in the relay apparatus is the same as that extended from the first embodiment to the present embodiment. It is possible to effectively acquire space diversity by changing the execution unit.

  Further, although the case has been described with the present embodiment where the encoding process is performed in the frequency domain, the encoding process may be performed in the time domain as in the first embodiment. In any case, the above effect (space diversity effect) can be obtained. Further, encoding may be performed for each hop in a region different from the time region and the frequency region.

Embodiment 3 FIG.
FIG. 9 is a diagram illustrating a configuration example of a third embodiment of the wireless communication system according to the present invention. As illustrated, the wireless communication system according to the present embodiment includes a plurality of communication devices 1-1 and 1-2 on the transmission side, a communication device 1b on the reception side, and a plurality of relaying signals between these communication devices. It comprises relay devices 2-1 to 2-6. In this embodiment, a radio communication system having a configuration in which a plurality of communication devices on the transmission side exist and a communication device on the reception side includes a plurality of antennas will be described. Specifically, the communication devices 1-1 and 1-2 are used as transmission-side communication devices, the communication device 1b is used as a reception-side communication device, and signals transmitted from the communication devices 1-1 and 1-2 are relayed. The devices 2-1 to 2-4 receive and relay the signals, and further, the relay devices 2-5 and 2-6 receive and relay the signals relayed by the relay devices 2-1 to 2-4. An operation when the communication device 1b receives signals relayed by the devices 2-5 and 2-6 will be described.

  The internal configuration of the communication devices 1-1 and 1-2 on the transmission side and the basic operation of each component are the same as those of the communication device 1 described in the first embodiment (see FIG. 2 and the like). Further, the internal configuration of relay apparatuses 2-1 to 2-6 and the basic operation of each component are the same as those of relay apparatus 2 described in the first embodiment (see FIG. 3 and the like). That is, in the wireless communication system of the present embodiment, each relay apparatus performs encoding processing in the time domain. As in the second embodiment, the encoding process may be executed in the frequency domain.

  FIG. 10 is a diagram illustrating a configuration example of the communication device 1b on the reception side of the wireless communication system illustrated in FIG. As illustrated, the communication device 1b includes two antennas 11-1 and 11-2, a receiving unit 12b, and a transmitting unit 13b. The signal line 14-1 is connected to the antenna 11-1, the receiving unit 12b, and the transmitting unit 13b, and the signal line 14-2 is connected to the antenna 11-2, the receiving unit 12b, and the transmitting unit 13b. In the communication apparatus 1b, when receiving a signal, the signal received from the antenna 11-1 is received via the signal line 14-1, and the signal received from the antenna 11-2 is received via the signal line 14-2. 12b, and a predetermined reception process is performed. When transmitting a signal, the transmission unit 13b generates a transmission signal and transmits the signal to the antenna 11-1 via the signal line 14-1 and to the antenna 11-2 via the signal line 14-2. The antennas 11-1 and 11-2 transmit the signal received from the transmission unit 13b.

  A signal transmission operation in the wireless communication system of the present embodiment will be described with reference to FIG. FIG. 11 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the present embodiment, and illustrates a signal transmission operation from the communication devices 1-1 and 1-2 in FIG. 9 to the communication device 1b. Note that the processes in steps S11b to S18b in FIG. 11 correspond to the processes in steps S11 to S18 described in the first embodiment. However, in the wireless communication system of the present embodiment, 8 symbols are handled as a set of signal vectors.

First, the communication devices 1-1 and 1-2 generate and transmit a signal (step S11b). Specifically, in the communication apparatuses 1-1 and 1-2, the transmission unit 13 generates a signal, transmits the signal to the antenna 11 from the signal line 14, and transmits the signal from the antenna 11. Here, the transmission unit 13 of the communication apparatus 1-1 uses the baseband signal as s ₁ ⁽¹⁾ = [s _1,1 ⁽¹⁾ , s _1,2 ⁽¹⁾ , s _1,3 ⁽¹⁾ , s _{1 , 4} ⁽¹⁾ , s _1,5 ⁽¹⁾ , s _1,6 ⁽¹⁾ , s _1,7 ⁽¹⁾ , s _1,8 ⁽¹⁾ ] ^T is generated and transmitted by the communication device 1-2 S ₂ ⁽¹⁾ = [s _2,1 ⁽¹⁾ , s _2,2 ⁽¹⁾ , s _2,3 ⁽¹⁾ , s _2,4 ⁽¹⁾ , s _2,5 ⁽¹⁾ , s _2,6 ⁽¹⁾ , s _2,7 ⁽¹⁾ , s _2,8 ⁽¹⁾ ] ^T shall be generated.

The j-th (j = 1 to 4) relay devices (relay devices 2-1 to 2-4) that receive signals at the first hop receive the signals transmitted from the communication devices 1-1 and 1-2, respectively. (Step S12b). Specifically, the relay devices 2-1 to 2-4 receive a signal from the antenna 21, and the signal is transmitted to the receiving unit 22 via the signal line 25. The receiving unit 22 performs predetermined reception processing on the received signal, and receives a received signal vector r _j ⁽¹⁾ = [r _{j, 1} ⁽¹⁾ , r _{j, 2} ⁽¹⁾ , which is a baseband signal. r _{j, 3} ⁽¹⁾ , r _{j, 4} ⁽¹⁾ , r _{j, 5} ⁽¹⁾ , r _{j, 6} ⁽¹⁾ , r _{j, 7} ⁽¹⁾ , r _{j, 8} ⁽¹⁾ ] ^T obtain. Each received signal r _{j, p} ⁽¹⁾ (p = 1 to 8) is given by the following equation (25).

Here, h _ji ⁽¹⁾ is the j-th (j = 1 to 4) relay device (relay device 2) from the i-th (i = 1, 2) communication device (communication devices 1-1, 1-2). -1 to 2-4) represent impulse responses of transmission lines. N _{j, p} ⁽¹⁾ is noise added to the signal h _j1 ⁽¹⁾ s _{1, p} ⁽¹⁾ + h _j2 ⁽¹⁾ s _{2, p} ⁽¹⁾ in the j-th repeater. The obtained signal of the above formula (25) is transmitted to the encoding unit 24 via the signal line 26, and the encoding unit 24 performs encoding (step S13b).

  The encoding process executed in step S13b will be described in detail.

In the encoding unit 24 of the relay apparatus 2-1, r ₁ ⁽¹⁾ = [r _1,1 ⁽¹⁾ , r _1,2 ⁽¹⁾ , r _1,3 ⁽¹⁾ , r _1,4 ^(1), performs encoding with respect to ^{_{r 1,5 (1), r 1,6}} (1), r 1,7 (1), r 1,8 (1)] T, the following A transmission signal vector s ₁ ^{(2) represented} by Expression (26) is obtained.

Further, in the encoding unit 24 of the relay apparatus 2-2, r ₂ ⁽¹⁾ = [r _2,1 ⁽¹⁾ , r _2,2 ⁽¹⁾ , r _2,3 ^{(1 _{), r 2,4 (1),}} r 2,5 (1), r 2,6 (1), r 2,7 (1), performs encoding with respect to r _2,8 ^{(1)] T} Then, a transmission signal vector s ₂ ^{(2) represented} by the following equation (27 ⁾ is obtained.

Further, in the encoding unit 24 of the relay apparatus 2-3, r ₃ ⁽¹⁾ = [r _3,1 ⁽¹⁾ , r _3,2 ⁽¹⁾ , r _3,3 ^{(1 _{), r 3,4 (1),}} r 3,5 (1), r 3,6 (1), r 3,7 (1), performs encoding with respect to r _3,8 ^{(1)] T} Then, a transmission signal vector s ₃ ^{(2) represented} by the following equation (28 ⁾ is obtained.

In the encoding unit 24 of the relay apparatus 2-4, r ₄ ⁽¹⁾ = [r _4,1 ⁽¹⁾ , r _4,2 ⁽¹⁾ , r _4,3 ^{(1 _{), r 4,4 (1),}} r 4,5 (1), r 4,6 (1), r 4,7 (1), performs encoding with respect to r _4,8 ^{(1)] T} The transmission signal vector s ₄ ⁽²⁾ expressed by the following equation (29 ⁾ is obtained.

Here, in the encoding unit 24 of the relay apparatuses 2-1 to 2-4, the four input signal vectors (r ₁ ⁽¹⁾ , r ₂ ⁽¹⁾ , r ₃ ⁽¹⁾ , r ₄ ⁽¹⁾ ) are described. Respectively, a signal vector equivalent to the case where pseudo orthogonal space-time coding is performed is generated. That is, each encoding unit 24 of each relay apparatus cooperates to perform pseudo orthogonal space-time encoding. Note that the coefficient (1/2) multiplied in the encoding process in each encoding unit 24 is the same as the encoding process in the encoding unit 24 and the encoding unit 24a described in the previous embodiment. The purpose is to normalize the total transmission power from each relay device that relays (at the first hop). Since the number of relay apparatuses is four at the first hop in this embodiment, the coefficient is multiplied by a coefficient different from that in the previous embodiment (when the number of relay apparatuses is two).

Respective transmission signals s _i ⁽²⁾ = [s _{i, 1} ⁽²⁾ , s _{i, 2} ⁽²⁾ obtained by the encoding unit 24 of the relay apparatuses 2-1 to 2-4 executing the encoding , S _{i, 3} ⁽²⁾ , s _{i, 4} ⁽²⁾ , s _{i, 5} ⁽²⁾ , s _{i, 6} ⁽²⁾ , s _{i, 7} ⁽²⁾ , s _{i, 8} ⁽²⁾ ] ^T (i = 1 to 4) are transmitted to the transmission unit 23 via the signal line 27, and after transmission processing is performed by the transmission unit 23, are transmitted via the signal line 25 and the antenna 21 (step S14b). .

The second-hop j-th (j = 1, 2) relay device (relay devices 2-5, 2-6) that receives the signal transmitted in step S14b is the first-hop relay device 2-1. Each of the signals transmitted from 2-4 is received (step S15b). Specifically, the relay devices 2-5 and 2-6 receive a signal from the antenna 21, and the signal is transmitted to the receiving unit 22 via the signal line 25. The receiving unit 22 performs predetermined reception processing on the received signal, and receives a received signal vector r _j ⁽²⁾ = [r _{j, 1} ⁽²⁾ , r _{j, 2} ⁽²⁾ , which is a baseband signal. r _{j, 3} ⁽²⁾ , r _{j, 4} ⁽²⁾ , r _{j, 5} ⁽²⁾ , r _{j, 6} ⁽²⁾ , r _{j, 7} ⁽²⁾ , r _{j, 8} ⁽²⁾ ] ^T obtain. Each received signal r _{j, p} ⁽²⁾ (p = 1 to 8) is given by the following equation (30).

Here, h _ji ⁽²⁾ receives the signal at the second hop from the i-th (i = 1 to 4) relay device (relay devices 2-1 to 2-4) that transfers the signal at the first hop. Represents the impulse response of the transmission path to the jth (j = 1, 2) relay device (relay devices 2-5, 2-6), and n _{j, p} ⁽²⁾ is a signal at the jth relay device. h _j1 ⁽²⁾ s _{1, p} ⁽²⁾ + h _j2 ⁽²⁾ s _{2, p} ⁽²⁾ + h _j3 ⁽²⁾ s _{3, p} ⁽²⁾ + h _j4 ⁽²⁾ s _{4, p} ⁽²⁾ Noise. The obtained signal of the above equation (30) is transmitted to the encoding unit 24 via the signal line 26, and the encoding unit 24 performs encoding (step S16b).

  The encoding process executed in step S16b will be described in detail.

In the encoding unit 24 of the relay device 2-5, r ₁ ⁽²⁾ = [r _1,1 ⁽²⁾ , r _1,2 ⁽²⁾ , r _1,3 ⁽²⁾ , ^{_{r 1,4 (2), r 1,5}} (2), r 1,6 (2), r 1,7 (2), performs encoding on r _1,8 ^{(2)] T,} the following A transmission signal vector s ₁ ^{(3) represented} by Expression (31) is obtained.

In the encoding unit 24 of the relay apparatus 2-6, r ₂ ⁽²⁾ = [r _2,1 ⁽²⁾ , r _2,2 ⁽²⁾ , r _2,3 ^{(2 _{), r 2,4 (2),}} r 2,5 (2), r 2,6 (2), r 2,7 (2), performs encoding on r _2,8 ^{(2)] T} The transmission signal vector s ₂ ^{(3) represented} by the following equation (32 ⁾ is obtained.

Here, in the encoding units 24 of the relay apparatuses 2-5 and 2-6, a space-time code having four symbols as a unit for the _two input signal vectors (r ₁ ⁽²⁾ , r ₂ ⁽²⁾ ). A signal vector equivalent to the case where the conversion is performed is generated. As described above, in the present embodiment as well as in the first and second embodiments, each hop relay apparatus changes the range to be processed in space-time coding (the unit of symbols for space-time coding). . Note that the coefficient (1 / √2) multiplied by the encoding process in each encoding unit 24 of the relay apparatuses 2-5 and 2-6 is the encoding unit 24 or encoding described in the previous embodiment. Similar to the encoding process in the unit 24a, the purpose is to normalize the total transmission power from each relay apparatus that performs relay simultaneously (at the second hop).

Respective transmission signals s _i ⁽³⁾ = [s _{i, 1} ⁽³⁾ , s _{i, 2} ⁽³⁾ obtained by the encoding units 24 of the relay apparatuses 2-5 and 2-6 executing the encoding , S _{i, 3} ⁽³⁾ , s _{i, 4} ⁽³⁾ ] ^T (i = 1, 2) are transmitted to the transmission unit 23 via the signal line 27 and subjected to transmission processing by the transmission unit 23. The signal is transmitted via the signal line 25 and the antenna 21 (step S17b).

  And the communication apparatus 1b which is a communication apparatus of the receiving side receives the signal transmitted by said step S17b, ie, the signal each transmitted from the 2nd hop relay apparatus 2-5, 2-6 (step S18b). .

The operation of the communication device 1b in step S18b will be described in more detail. In the communication device 1b, a signal received by the antenna 11-1 is transmitted to the receiving unit 12b via the signal line 14-1, and the antenna 11- 2 is transmitted to the receiver 12b via the signal line 14-2. The receiving unit 12 performs predetermined reception processing on each received signal, and receives signal vectors r _j ⁽³⁾ = [r _{j, 1} ⁽³⁾ , r _{j, 2} ⁽³⁾ which are baseband signals. , R _{j, 3} ⁽³⁾ , r _{j, 4} ⁽³⁾ , r _{j, 5} ⁽³⁾ , r _{j, 6} ⁽³⁾ , r _{j, 7} ⁽³⁾ , r _{j, 8} ⁽³⁾ ] ^T (j = 1,2) is obtained. Each received signal r _{j, p} ⁽⁴⁾ (p = 1 to 8) is given by the following equation (33).

Here, h _ji ⁽³⁾ is transferred from the i-th (i = 1, 2) relay device (relay devices 2-5, 2-6) that transfers signals at the second hop to the j-th ( j = 1,2) represents the impulse response of the transmission path to the antenna (antennas 11-1, 11-2), and n _{j, p} ⁽³⁾ is the signal h _j1 ⁽³⁾ s _{1, p} ⁽³⁾ + h _j2 ⁽³⁾ Noise added to s _{2, p} ⁽³⁾ .

Subsequently, characteristic operations in the wireless communication system of the present embodiment will be described. When the relay apparatuses 2-1 to 2-6 execute the signal relay process including the encoding process described above, the received signal vector r _j received by the communication apparatus 1b with the j-th (j = 1, 2) antenna. ⁽³⁾ can be expressed as the following equation (34).

At this time, the signal block S of Expression (34) is the same as the signal block S of the received signal vector (see Expression (8)) received by the communication device 1-2 on the reception side of the wireless communication system shown in Embodiment 1. Similarly, it has a structure equivalent to a quasi-orthogonal space-time code. Therefore, it is possible to obtain space diversity that has an effect of reducing the influence of attenuation on the signal of the propagation path. Then, when receiving processing such as maximum likelihood determination reception is performed on the received signal vector r _j ⁽³⁾ , it is possible to perform highly reliable determination as compared to the case where the diversity is not obtained. it can.

  Note that, as a modification of the wireless communication system of FIG. 9 described in the present embodiment, a wireless communication system having the configuration shown in FIG. 12 is conceivable. The wireless communication system in FIG. 12 replaces the communication apparatuses 1-1 and 1-2 in FIG. 9 with a communication apparatus 1b-1 having a plurality of (two) antennas having the same configuration as that on the reception side as a communication apparatus on the transmission side. As prepared. The internal configuration of the communication devices 1b-1 and 1b-2 in FIG. 12 and the basic operation of each component are the same as those of the communication device 1b shown in FIG. 9 (see FIG. 10 and the like). In the wireless communication system of FIG. 12, the communication device 1b-1 on the transmission side transmits different data (signals) from the antennas 11-1 and 11-2. That is, the only difference from the wireless communication system in FIG. 9 is whether different data is transmitted from a plurality of communication devices or different data is transmitted from a plurality of antennas of a single communication device. Since the operation is performed, the same diversity effect can be obtained in the communication devices (1b, 1b-2) on the receiving side.

  Further, as a modified example different from FIG. 12, a wireless communication system having the configuration shown in FIG. 13 is conceivable. The wireless communication system in FIG. 13 includes a relay device 2b having a plurality of (four) antennas instead of the first-hop relay devices 2-1 to 2-3 in FIG. The configuration of the relay device 2b is, for example, as shown in FIG. 14, and the antennas 21-1 to 21-4 and signals received by the respective antennas are received via the signal lines 25-1 to 25-4, and reception processing is performed. A receiving unit 22b, an encoding unit 24b that encodes a signal received from the receiving unit 22b via the signal line 26, and a transmitting unit 23b that performs transmission processing on the signal received from the encoding unit 24b via the signal line 27 With.

Here, in the encoding unit 24b, the encoding units 24 of the relay apparatuses 2-1 to 2-4 in FIGS. 9 and 12 perform the above-described signal r _j ⁽¹⁾ = [r _{j, 1} ⁽¹⁾ , r _{j , 2} ⁽¹⁾ , r _{j, 3} ⁽¹⁾ , r _{j, 4} ⁽¹⁾ , r _{j, 5} ⁽¹⁾ , r _{j, 6} ⁽¹⁾ , r _{j, 7} ⁽¹⁾ , r _{j, 8} ⁽¹⁾ ] The same processing as the encoding for ^T (j = 1 to 4) is performed. That is, in the encoding unit 24b, the respective signal vectors received by the receiving antennas 21-1 to 21-4 are encoded by the first-hop relay apparatuses 2-1 to 2-4 in FIG. 9 and FIG. To do. The respective signal vectors obtained by executing the encoding are transmitted to different antennas after being subjected to predetermined transmission processing by the transmission unit 23b, and are transmitted to the second hop relay devices 2-5 and 2-6, respectively. Sent to. Even in the radio communication system having such a configuration, the same effect as that of the radio communication system of FIG. 9 can be obtained.

  As described above, in the present embodiment, even when the number of relay devices and the number of antennas that cooperate in transmission / reception processing at each hop increase, it is effective by making the corresponding encoding processing in the relay device correspond. It was shown that space diversity can be obtained. In addition, it has been shown that the same effect as in the previous embodiment can be obtained even when performing spatial multiplexing transmission in which there are a plurality of signal vectors to be transmitted. Moreover, it was shown that the same effect can be obtained by operating a communication device and a relay device having a plurality of antennas instead of operating a plurality of communication devices and a relay device simultaneously.

  As described above, in the wireless communication system according to the present embodiment, different signals (data) are simultaneously transmitted from a plurality of devices or antennas, and these signals are transferred a plurality of times via a plurality of relay devices or a plurality of antennas. In each relay process executed simultaneously (with the same hop), the received signal is space-time encoded and transferred. In addition, encoding is performed in each relay process so that the communication device on the receiving side that finally receives the signal receives a signal (signal block) having a structure equivalent to the pseudo orthogonal space-time code. Even in such a case, the same effect as the wireless communication system of the previous embodiment can be obtained.

Embodiment 4 FIG.
FIG. 15 is a diagram illustrating a configuration example of a fourth embodiment of the wireless communication system according to the present invention. As illustrated, the wireless communication system according to the present embodiment includes a communication device 1b on the transmission side, a communication device 1 on the reception side, and a plurality of relay devices 2-1 that relay signals between these communication devices, and 2-2.

  The internal configuration of the communication device 1b including a plurality (two) of antennas is the same as that of the communication device 1b (see FIG. 10) described in the third embodiment. However, in communication apparatus 1b of the present embodiment, a signal is transmitted after performing the same encoding process as the first-hop relay apparatus described in the previous embodiment. In the present embodiment, the case where the encoding process is performed by the transmission unit 13b will be described. However, as in the relay apparatus, an encoding unit may be provided and performed.

  The internal configuration of the communication device 1 on the receiving side and the basic operation of each component are the same as those of the communication devices described in the first embodiment (see FIG. 2 and the like), and the relay devices 2-1 and 2-2. The internal configuration and the basic operation of each component are the same as those of each relay device described in the first embodiment (see FIG. 3 and the like).

  In the present embodiment, a wireless communication system in which a communication device on a transmission side includes a plurality of antennas, performs transmission after space-time coding at the time of data transmission, and relays the signal by a plurality of relay devices. explain. As in the second embodiment, the encoding process may be executed in the frequency domain.

  A signal transmission operation in the wireless communication system of the present embodiment will be described with reference to FIG. FIG. 16 is a flowchart illustrating an example of a signal transmission operation in the wireless communication system according to the present embodiment, and illustrates a signal transmission operation from the communication device 1b to the communication device 1 in FIG. In the radio communication system according to the present embodiment, four symbols are handled as a set of signal vectors as in the radio communication system according to the first embodiment.

  First, the communication device 1b generates and transmits a signal (step S11c). Specifically, the transmission unit 13b generates a signal, transmits the signal to the antennas 11-1 and 11-2 through the signal lines 14-1 and 14-2, and transmits the signal from the antennas 11-1 and 11-2. At this time, the transmission unit 13b generates a baseband signal and further performs space-time coding to generate a signal represented by the following equation (35) (base-space coded baseband signal). And transmitted to the antennas 11-1 and 11-2, respectively. This encoding process is equivalent to the encoding process executed by each first-hop relay device in the wireless communication system according to the first embodiment.

The j-th (j = 1, 2) relay devices (relay devices 2-1 and 2-2) that receive signals at the first hop receive signals transmitted from the respective antennas of the communication device 1b (steps). S31). Specifically, the relay apparatuses 2-1 and 2-2 receive a signal from the antenna 21, and the signal is transmitted to the receiving unit 22 via the signal line 25. The receiving unit 22 performs predetermined reception processing on the received signal, and receives a received signal vector r _j ⁽¹⁾ = [r _{j, 1} ⁽¹⁾ , r _{j, 2} ⁽¹⁾ , which is a baseband signal. r _{j, 3} ⁽¹⁾ , r _{j, 4} ⁽¹⁾ ] ^T is obtained. Each received signal r _{j, p} ⁽¹⁾ (p = 1 to 4) is given by the following equation (36).

Here, h _ji ⁽¹⁾ is the j-th (j = 1, 2) relay device (relay) from the i-th (i = 1, 2) antenna (antenna 11-1, 11-2) of the communication device 1b. It represents the impulse response of the transmission line to the devices 2-1 and 2-2). N _{j, p} ⁽¹⁾ is noise added to the signal h _j1 ⁽¹⁾ s _{1, p} ⁽¹⁾ + h _j2 ⁽¹⁾ s _{2, p} ⁽¹⁾ in the j-th repeater. The obtained signal of the above expression (36) is transmitted to the encoding unit 24 via the signal line 26, and the encoding unit 24 performs encoding (step S32).

  The encoding process executed in step S32 will be described in detail.

In the encoding unit 24 of the relay apparatus 2-1, r ₁ ⁽¹⁾ = [r _1,1 ⁽¹⁾ , r _1,2 ⁽¹⁾ , r _1,3 ⁽¹⁾ , r _1,4 ⁽¹⁾ ] ^{T is} encoded to obtain a transmission signal vector s ₁ ^{(2) represented} by the following equation (37).

Further, in the encoding unit 24 of the relay apparatus 2-2, r ₂ ⁽¹⁾ = [r _2,1 ⁽¹⁾ , r _2,2 ⁽¹⁾ , r _2,3 ^{(1 )} , R _2,4 ⁽¹⁾ ] ^{T is} encoded to obtain a transmission signal vector s ₂ ^{(2) represented} by the following equation (38).

Here, in the encoding units 24 of the relay apparatuses 2-1 and 2-2, a space-time code having two symbols as a unit for the two input signal vectors (r ₁ ⁽²⁾ , r ₂ ⁽²⁾ ). A signal vector equivalent to the case where the conversion is performed is generated. That is, the encoding units 24 of the relay devices cooperate to perform space-time encoding in units of 2 symbols. As described above, the range (unit of execution) of the encoding process can be changed by the space-time coding executed by each relay device that performs relaying simultaneously with the space-time coding executed by the communication device 1b on the transmission side. This is a feature of the wireless communication system of the present embodiment. Thereby, each relay apparatus can relay and transmit a signal to the communication apparatus 1 on the receiving side while maintaining the orthogonality of each signal transmitted from the communication apparatus 1b. Note that the coefficient (1 / √2) multiplied by the encoding process in each encoding unit 24 is the total from each relay apparatus that performs relay simultaneously, as in the encoding process described in the previous embodiment. The purpose is to normalize the transmission power.

Respective transmission signals s _i ⁽²⁾ = [s _{i, 1} ⁽²⁾ , s _{i, 2} ⁽²⁾ obtained by encoding by the encoding units 24 of the relay apparatuses 2-1 and 2-2. , S _{i, 3} ⁽²⁾ , s _{i, 4} ⁽²⁾ ] ^T (i = 1, 2) are transmitted to the transmission unit 23 via the signal line 27 and subjected to transmission processing by the transmission unit 23. Then, it is transmitted via the signal line 25 and the antenna 21 (step S33).

  And the communication apparatus 1 which is a communication apparatus of the receiving side receives the signal transmitted by said step S33, ie, the signal each transmitted from the relay apparatus 2-1 and 2-2 of the 1st hop (step S18c). .

The operation of the communication device 1 in step S18c will be described in more detail. In the communication device 1, a signal received by the antenna 11 is transmitted to the receiving unit 12 via the signal line 14. The receiving unit 12 performs predetermined reception processing on the signal received from the antenna 11 and receives a received signal vector r ₁ ⁽²⁾ = [r _1,1 ⁽²⁾ , r _1,2 ^{( 2)} , r _1,3 ⁽²⁾ , r _1,4 ⁽²⁾ ] ^T Each received signal r _{1, p} ⁽²⁾ (p = 1 to 4) is given by the following equation (39).

Here, h _ji ⁽²⁾ represents the impulse response of the transmission path from the i-th (i = 1, 2) relay device (relay devices 2-1 and 2-2) that transfers signals to the communication device 1. N _{j, p} ⁽²⁾ is noise added to the signal h _j1 ⁽²⁾ s _{1, p} ⁽²⁾ + h _j2 ⁽²⁾ s _{2, p} ⁽²⁾ in the communication device 1.

Subsequently, characteristic operations in the wireless communication system of the present embodiment will be described. The communication apparatus 1b on the transmission side executes the signal transmission process including the above-described encoding process (a process equivalent to the encoding process executed by each relay apparatus at the first hop in the first embodiment), and further the relay apparatus 2 -1 and 2-2 execute the signal relay process including the encoding process described above, so that the received signal vector r ₁ ⁽²⁾ received by the receiving-side communication device 1 is expressed by the following equation (40). Can be represented.

At this time, the signal block S of Expression (40) is the same as the signal block S of the received signal vector (see Expression (8)) received by the communication device 1-2 on the reception side of the wireless communication system shown in Embodiment 1. Similarly, it has a structure equivalent to a quasi-orthogonal space-time code. Therefore, it is possible to obtain space diversity that has an effect of reducing the influence of attenuation on the signal of the propagation path. When receiving processing such as maximum likelihood determination reception is performed on the received signal vector r ₁ ⁽²⁾ , it is possible to perform highly reliable determination as compared to the case where diversity is not obtained. it can.

  In the present embodiment, a case has been described in which the transmitting apparatus 1b transmits a signal subjected to space-time coding. However, space-frequency coding (SFBC) may be performed. Good. In addition, an example in which the number of signal relays by the relay device is 1 (1 hop) has been described, but it is similar to the case where the wireless communication system of the first embodiment is extended to the wireless communication system of the second embodiment. It is possible to extend the number of signal relays to two or more by this method.

  As described above, in the present embodiment, the communication device 1b having a plurality of antennas, which is the communication device of the transmission source, transmits a signal on which space-time coding has been performed, and the signal transmitted from the communication device 1b. Each relay device that relays the above performs a cooperative operation and performs space-time coding in a unit different from the coding processing in the communication device 1b. Also in the radio communication system having such a configuration, the same effects as those of the first to third embodiments can be obtained, and the communication quality can be improved. Further, since each relay device does not need to separate signals, it is possible to prevent the number of devices from increasing and the processing complexity.

  As described above, the present invention is useful as a wireless communication system in which a relay device relays a signal between these communication devices when the communication device on the transmission side and the communication device on the reception side cannot communicate directly, In particular, it is suitable for a wireless communication system that provides high-quality communication while preventing an increase in the number of relay devices.

1, 1a, 1b, 1-1, 1a-1, 1-2, 1a-2, 1b-1, 1b-2 Wireless communication apparatus (communication apparatus)
2, 2a, 2b, 2-1 to 2-4, 2a-1 to 2a-6 Wireless communication relay device (relay device)
11, 11-1, 11-2 to 11-4, 21, 21-1 to 21-4 Antenna 12, 12a, 12b, 22, 22a, 22b Receiving unit 13, 13a, 13b, 23, 23a, 23b Transmitting unit 14, 25, 26, 27, 14-1, 14-2, 25-1 to 25-4 Signal line 24, 24a Encoding unit

Claims (7)

A wireless communication system for relaying a signal transmitted from a first wireless communication device by a plurality of wireless communication relay devices and transmitting the signal to a second wireless communication device,
Each of the plurality of wireless communication relay devices cooperates with another wireless communication relay device when relaying a received signal, and the second wireless communication device obtains space diversity at the nth time (n: normal The wireless communication relay apparatus that relays the received signal in space-time coding, space-frequency coding, and time in units of symbols different from those of other wireless communication relay apparatuses that perform relays other than the nth time. A wireless communication system characterized by rearranging or rearranging on the frequency . The first wireless communication device includes a plurality of wireless communication devices,
The wireless communication system according to claim 1, wherein each of the plurality of wireless communication devices transmits a different signal. The first wireless communication device includes a plurality of antennas;
The first wireless communication apparatus, a wireless communication system according to claim 1, characterized by transmitting a different signal from each antenna. The first wireless communication device performs space-time coding or space-frequency coding in a different number of symbols from the plurality of wireless communication relay devices, and transmits a signal obtained as a result thereof. Item 4. The wireless communication system according to Item 3 . The wireless communication system according to any one of claims 1 to 4 , wherein the second wireless communication device includes a plurality of antennas. The wireless communication relay device in a wireless communication system that relays a signal transmitted from a first wireless communication device by a plurality of wireless communication relay devices and transmits the signal to a second wireless communication device,
When transferring a received signal, when performing relay for the nth time (n: positive integer) so that space diversity can be obtained in the second wireless communication device in cooperation with another wireless communication relay device , Performs space-time coding, space-frequency coding, time reordering, or frequency reordering of received signals in a different number of symbols from other wireless communication repeaters that perform relays other than the nth time A wireless communication relay device. When the first wireless communication apparatus includes a plurality of antennas and transmits a signal on which space-time coding or space-frequency coding is performed,
The radio communication relay apparatus according to claim 6 , wherein the reception signal is encoded in a unit of a number of symbols different from the encoding process in the first radio communication apparatus.

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